1. Field of Invention
The present invention relates to a medical wire introducer, and more particularly, to a protective sheath assembly for introducing a wide variety of balloon catheters into blood vessels. The present invention also relates to a wire introducer/protective sheath assembly and methods of constructing and using same.
2. Description of Related Art
Minimally invasive surgical techniques, including intravascular techniques such as angioplasty, have had a rapid development and wide acceptance within the medical fields. In these surgical procedures, usually a percutaneous or arterial sheath is introduced through a puncture or an incision in the patient's skin to provide percutaneous access to blood vessels. This step is followed by insertion of a catheter through the arterial sheath and its advancement through the arteries to target sites. The catheter can be equipped with different devices at its distal end, such as a balloon. These devices can serve a variety of functions, such as occluding the vessel so as to block blood flow, and dilating occluded blood vessels during angioplasty. Solid or hollow thin wires, called guidewires, are commonly used to guide the insertion of catheters.
Angioplasty balloon catheters can be roughly divided into three categories: over-the-wire (OTW) systems, single-operator-exchange (SOE) or monorail systems, and fixed-wire systems (also called "balloon-on-a-wire"). In an OTW system, a solid guidewire is used to guide a balloon catheter, which is tracked coaxially over the guidewire and can be moved relative to it. SOE balloon catheters are modified OTW catheters, i.e., only the distal portion of a SOE balloon catheter tracks coaxially over the guidewire. In a fixed-wire system, a hollow guidewire is in fluid communication with a balloon mounted at its distal end to supply inflation fluid to the balloon. The guidewire typically has a soft tip at its distal end to guide the placement in the vessel.
Vascular access may include a femoral approach, a brachial approach or a radial approach. A commonly adopted procedure for intravascular surgery through a femoral approach typically involves the following steps: (a) identifying the femoral artery and administrating local anesthetic to the patient; (b) inserting a needle into the femoral artery (or an appropriate peripheral blood vessel) and waiting for blood to flow out through the needle; (c) introducing a guidewire into the blood vessel through the needle and then removing the needle leaving the guidewire in place within the blood vessel; (d) tracking an arterial (percutaneous) sheath and dilator over the guidewire into the blood vessel, so that the distal end of the arterial sheath enters the vessel; (e) removing the dilator and the guidewire leaving the arterial sheath in place; (f) introducing a guide catheter over a guidewire through the percutaneous sheath and advancing it around the aortic arch; (g) removing the guidewire; (h) connecting the guide catheter to an inflation device and a steering tool through a Y-adaptor and/or to a manifold assembly through another Y-adaptor, with the manifold assembly usually being connected to a pressure transducer and a syringe; (i) introducing a catheter over a guidewire through the guide catheter and the Y-adaptor, and advancing it through the arteries until the distal end of the catheter reaches the treatment site. Alternatively, if a "balloon-on-wire" catheter, such as a distal occlusion wire (DOW), is being used in the last step the catheter may be directly inserted into the blood vessel through the guide catheter and Y-adaptor.
Obviously, during this process, blood may bleed back under arterial pressure. In order to avoid excess bleeding and possible air embolisms, a hemostasis valve or a Touhy-Borst valve is usually installed in the Y-adaptor. Various hemostasis valves have been developed. A hemostasis valve is typically composed of one or more resilient, cylindrical pieces having slits or holes therethrough. These slits and/or holes are sized and configured so that they are normally closed, but may permit a guidewire or a catheter to be forced through while maintaining a seal around the guidewire or catheter.
However, when a fixed-wire catheter, such as a DOW, is used, it becomes very difficult to insert the catheter through a hemostasis valve because the distal end of a "balloon-on-wire" catheter usually has a soft tip to guide the catheter while preventing damage to the blood vessel. A concomitant problem of having a balloon with a soft tip, however, is that the soft tip is capable of being damaged while inserting it through the hemostasis valve. Thus, there is a further need for a protective sheath to shield the balloon and the soft tip when introducing the same through a hemostasis valve.
Presently, either a guidewire needle introducer or a protective sheath, is separately used to introduce a balloon catheter into a guide catheter via a hemostasis valve mounted within the Y-adaptor. However, when using either procedure, the problem of back blood flow still exists as the hollow protective sheath, or the large needle, is inserted into the Y-adaptor. For some catheter devices of the balloon-on-wire type, such as a DOW, these methods, i.e., using either a protective sheath or a large needle introducer, also will be very cumbersome, time consuming, and cause greater back bleed. Thus, there exists an urgent need for an introducer device which can be conveniently and safely utilized to insert a balloon catheter or any-fixed wire devices during intravascular surgery.